Apparatus for measuring extrusion pressures



Patented June 19, 1951 APPARATUS FOR/MEASURING EXTRUSION PRESSURES George E. Gliss, Baltimore, Md., assignor to Western Electric Company,

Incorporated, New York,

N. Y., a corporation of New York Application April 25, 1947, Serial No. 743,915

Claims. 1

This invention relates to apparatus for measuring extrusion pressures, and more particularly to apparatus for measuring the pressure on material being extruded over conductors.

In the manufacture of the insulated and jacketed conductors, a conductor, which may be bare or covered, is sometimes advanced continuously through an extrusion head of an adjustable extruding apparatus of a type which includes an extrusion passage in which an extrusion die is mounted and in which a. core tube and a coretube-holder are positioned for centering the conductor with respect to the extrusion die. The extrusion apparatus forces insulating material into a covering around the conductor. The insulating material is brought to the extrusion apparatus in batches, and the extrudability of the batches of insulating material may vary one from another. When the extrudability varies, it necessitates readjusting the extrusion process for each batch of the insulating material varying in ex trudability from the preceding batch.

In the past, there has been no satisfactory means for determining the extrudability of each batch of insulating material without long experimentation, and the extrudability had to be determined by trial and error methods. One of the main reasons that the extrudability of batches of insulating material could not be ascertained was that there has been no means available for measuring the pressure of the insulating material as it was extruded. The high extrusion pressures of the insulating material in the extruding apparatus aggravated the problem since they made imperative pressure testing apparatus which would satisfactorily withstand these high pressures.

An object of the invention is to provide new and effective apparatus for measuring extrusion pressures.

A further object of the invention is to provide new and effective apparatus for measuring the extrusion pressure of material being extruded without interfering with the extrusion operation.

Still another object of the invention is to provide new and efl'ective apparatus for measuring extrusion pressures, which is designed to be used with known extruding apparatus without necessitating extensive modification of the extruding apparatus.

An apparatus illustrative of certain features of the invention includes a flask having a threaded portion designed to be screwed into an opening in an extrusion head and a ram designed to hold extrusion tools in place against the pressure of insulating material being forced through the extrusion head. A hydraulic system is provided for applying a predetermined pressure to the ram, and a gage serves to measure the pressure applied to the ram. The gage measures any increase in pressure of the hydraulic fluid due to the pressure exerted upon the ram by" the insulating material so that the pressure of the insulating material may be measured thereby.

A complete understanding of the invention may be obtained from the following detailed description, when read in conjunction with the append ing drawing, in which the only figure is a partially sectional view of an apparatus for measuring extrusion pressures illustrating certain features of the invention.

Referring now in detail to the drawing, there is shown therein a continuous extruding apparatus provided with pressure measuring apparatus illustrating certain features of the invention.

The continuous extruding apparatus is designed to apply a covering 8 of plastic material, such as, for example, compound including rubber or a rubber-like material, upona filamentary conductor 6, which may be bare or covered with a textile or plastic covering. This apparatus includes an extrusion cylinder l0 having a bore ll formed therein, in which a stock screw I2 is rotatably mounted. The stock screw is rotated by suitable driving means, such as an electric motor (not shown), to force the plastic material I! through an extruding head I 4 under high pressure. The extruding head includes a body memher Is having a bore IS in which is slidably mounted tool holder H, which abuts an end of the extrusion cylinder Ill. The tool holder has a tapered opening l8, which forms a continuation of the bore I I and communicates with an extrusion passage 20 formed therein. A tube 19 is carried by the head in alignment with the extrusion passage 20.

An annular die holder 2| mounted in the exit end of the extrusion passage 2|! in the tool holder I! has a bore 21 formed therein in which a forming die 23 is mounted. The conductor 6 is advanced toward the left, as viewed in the drawing, by suitable core-advancing means, such as a capstan (not shown), through a core-tubeholder 25 and a core tube 26. The core-tubeholder 25 is provided with an inclined surface 21 for deflecting the plastic material l3 toward the die 23, and an aligning plate 3| bolted to the tool holder l1 maintains the die holder 2| and the core-tube-holder 25, and thereby the core 'the cylinder as 23. aligned with each other A threaded portion 32 is provided in the bore l5 in the member |5 of the extrusion head l4, and thetool holder carryin the die holder 2|, the die 23, the coretube-holder 25, the core tube and the aligning plate 3| may be inserted into the bore Ii or be removed therefrom. V

A flask 4|! having a threaded neck'portion 4| is designed to be threaded into the threaded portion 22 of the bore It in the body member i5. A plunger 42 is mounted slidably in a bore 45 formed in the neck portion of the flask 45, and is designed to engage the tool holder I! when pressed upwardly, as viewed in the drawing, by a piston l of a hydraulic ram unit 41. The ram unit 41 is mounted in the flask II, and is secured therein by a plug of the flask 45. A cylinder 5| of the ram unit 41 is held against an annular shoulder 52 of the flask 40 by the plug 55, which is threaded into a tapered opening 55 formed in the flask. Rings 55-55 serve to center the cylinder 5| in the flask 40.

The flask 40 is provided with a slot 51 to provide clearance when the cylinder 5| is inserted in the flask 4|! for a pipe 58 communicating with the lower end of the cylinder 5|. A flexible hose I is connected to the pipe 58 and to a manually operable pump unit 5| of a well known type, and a pressure gage 62 is connected by a pipe 65 to the pipe 58. r

A flnger I5 fastened rigidly to the plunger 42 projects through a slot 1| formed in the flask 45, and engages a spring-loaded plunger I2 of a highsensitivity dial indicator 13 of a, well known type. The dial indicator includes a dial I4 calibrated in thousandths of an inch and a pointer 15 movable along the dial by the spring-loaded plunger 12. The dial indicator serves to indicate the relative positions up or down, as viewed in the drawing, in the extruding head of the die holder 2| tube 2 and the die in the extrusion passage 2|.

the die 22, the core-tube-holder 25, the core tube" 25 and aligning plate 3|.

In the operation of the apparatus described hereinabove, the die holder 2|, the die 22, the core-tube-holder 25, the core tube 26, and the aligning plate 3| are mounted in the tool holder H, which then is inserted into the bore |5 in the body member l5. The flask 45 with the plunger 42 is threaded into the threaded portion 32 of the bore l6, and the ram unit 41 is secured in the flask. The hose 55 then is connected to the pipe 55, and the manually operable pump unit 6| is actuated to supply a hydraulic fluid through the hose 50 and the pipe 58 into the lower end of viewed in the drawing. The fluid pumped into the lower end of the cylinder 5| moves the ram 45 from its broken line position to its full line position. The ram 4i'forces the plunger 42 upwardly, and forces the tool holder |1 against the end of the extruding cylinder II. In this position of the tool holder, the aligning plate 3|, the annular die holder 2 I, and the coretube-holder 25 are held in correct extruding po-' sitions. The dial indicator 13 indicates when-the tool holder is properly located in the bore IS.

The unit 5| is actuated until the indicator 62 reads zero, at which time the hydraulic liquid in the cylinder 5| will be under a predetermined pressure, and the pump unit 6| is actuated to prevent Insulating material I: is then introduced into the bore II in the extrusion cylinder I4, and the stock screw |2 is rotated to force the insulated material through the bore H and the opening" flow of the hydraulic liquid back thereto.

against the core-tube-holder 25, the core tube 26, the die holder 2|, the die 23, and the aligning plate I The total resultant force of the insulating material I! in a downward direction upon the tool holder I! is equal to the pressure of the material timm the area of the exit of the extruding cylinder III, which is known. Hence, this resultant force is directly proportional to the pressure on the insulating material. This force is transmitted by these elements to the plunger 42, which transmits it to the ram 46. The ram 45 transmits this force to the hydraulic liquid in the cylinder 5|, and this force increases the pressure on the hydraulic liquid in direct proportion to the pressure of the insulating material l3. The increase in pressure on the hydraulic liquid is indicated by the gage '2, which is calibrated in units of pressure of the insulating material. Hence, at any particular time while the insulating material I3 is being extruded, its extrusion pressure will be'shown directly on the gage 62. If desired, the gage 52 may be calibrated so that its zero point is indicated when there is no pressure on the hydraulic liquid, and an initial read ing obtained after the pump unit is actuated to locate the tool holder |'I correctly but before there is any component of pressure from the material to be extruded. The material may then be extruded and the pressure thereon at any time be determined by taking the reading at that time and subtracting the initial reading therefrom.

The above-described pressure measuring device serves to hold the tool holder in a position such that it holds the extruding tools, the die 22, the core-tube-holder 25, the core tube 26, in correct extruding positions in the extruding head H. The extruding head l4, the tool holder, the extruding tools and the extrusion cylinder III, which form a well known type of extruding apparatus need not be changed at all in structure to lit the extruding apparatus to the pressure measuring apparatus, as no adaptation is necessary. The pressure measuring apparatus -merely may be substituted for a retaining nut which ordinarily is threaded into the threaded opening 32 to hold the tool holder in correct extruding position in the head H. The extruding capability of the extruding apparatus is not impaired in the slightest by the addition of the pressure measuring apparatus thereto. Also, the entire pressure measuring device is separable and portable so that it may be used selectively with any of several extruding apparatus, if such use is found to be desirable for any reason.

The pressure measuring apparatus is simple in its structure and operation so that it requires a minimum maintenance. Furthermore, it occupies very little space and does not interfere in the slightest with extruding operations.

What is claimed is:

1. In an extruding apparatus including extruding tools, an extruding head having an extrusion opening therein, a threaded opening in communication with the extrusion opening to permit the extruding tools to be inserted in the extrusion passage and means for forcing plastic material through the extrusion passage, the improvement comprising a hydraulic cylinder having a threaded end portion designed to be threaded into the threaded opening in the extruding head, a piston mounted slidably with respect to the cylinder,,

means for forcing a liquid into one end of the cylinder to force the piston against extruding tools positioned in the extrusion opening in the ,of a hydraulic liquid for supporting the piston, GEORGE E. GLISS. and means responsive to changes of pressure on the hydraulic liquid for measuring the pressure REFERENCES CITED of the Plastic material bemg i 35 The following references are of record in the 4. In an extrusion apparatus including an file of t t extruding head having an extrusion passage and also being provided with a threaded opening 7 UNITED STATES PATENTS communicating with the passage, a device for Number Name Date measuring the pressure of plastic material forced 40 ,7 2 chatillon Oct. 13, 1931 through the passage which comprises a flask hav- 2,4 Jones n 4, 1949 ing a threaded neck portion designed to be TENT threaded into the threaded opening in the head, FOREIGN PA S a hydraulic cylinder mounted in the flask a Number Country Date extruding head to hold the extruded tools in connected operatively to the liquid in the cylinder extruding positions therein, and indicating means and projecting through the neck of the flask,

responsive to the pressure on the liquid for meassaid ram serving to transmit force from the plas uring the pressure of plastic material being forced tic material to the liquid, and means responsive through the extrusion opening. 5. to the pressure on the liquid for measuring the 2. In an extruding apparatus including an pressure on the plastic material. extruding head having an extrusion passage 5. In an extrusion apparatus including an therein and a bore commumcating from the exteextruding head having an extrusion opening means for forcing plastic material through the bore extending from the extrusion opening to extrusion bore, a pressure-measuring device which the exterior of the head, means for forcing plas- 3. In an extrusion apparatus including an the cylinder and having a threaded neck portion the combination of a cylinder, means having a. cylinder to force the ram against the tool holder slidably in the cylinder, means for transmitting measuring the component of the pressure on the force from plastic material extruded from the liquid due to the pressure on the plastic material. extrusion passage to the piston, a closed system hydraulic liquid confined in the cylinder, a an 4501070 Great Britain July 9, 1936 

